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MacBook 820-3332-A turns on ,,,, than off with 3 beeps..

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    #1

    MacBook 820-3332-A turns on ,,,, than off with 3 beeps..

    Working on this MacBook and have hit a wall... The laptop will actually turn on and start to load,, it will get to the apple logo and progress bar.. Eventually, it will turn off and back on and beep 3 times with a blank screen..

    I tested all the power rails per the schematic (provided) and these are the results..

    PM_SLP_S3_L =3.3v
    PP0V75_S0_DDRVTT = .67
    PP1V05_S0 = 1.05
    PP1V8_S0 =1.8
    PP3V3_S0 =3.3v
    PP3V3_S0GPU =3.3v
    PP3V3_S3 =3.3v
    PP3V3_S5 =3.3v
    PP3V3_S5_AVREF_SMC =3.3v
    PP3V42_G3H =3.4v
    PP5V_S0 =5.0v
    PP5V_S3 = 5v
    PP5V_S5 =5v.
    PPBUS_G3H =12.67
    PPDCIN_G3H =20v
    PPVCORE_GPU =.90v
    PPVCORE_S0_CPU =.82v
    PPVTTDDR_S3 =.68v

    The laptop will always turn on by itself when plugged in... With just the battery it will not.. Will check for a short to see if I can find why the laptop turns itself on... Any ideas would be appreciated and helpful...
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    #2
    Re: MacBook 820-3332-A turns on ,,,, than off with 3 beeps..

    Could the .67v actually be a bad RAM, or is .67 sufficient?
    Last edited by bjhawfam; 06-30-2018, 08:09 AM.

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      #3
      Re: MacBook 820-3332-A turns on ,,,, than off with 3 beeps..

      Strange thing is the laptop turned on this morning and let me install the OSX... Than the screen goes crazy and shuts off,,, video problem?.. Running the AHT mode to see if it reports any problems related to video or ram...
      Last edited by bjhawfam; 06-30-2018, 08:07 AM.

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        #4
        Re: MacBook 820-3332-A turns on ,,,, than off with 3 beeps..

        Update; ran the Apple Hardware Test (AHT) and got no errors.. The hardware tab shows the i7 with 8GB RAM and the Nvidia with 1 GB ... I did heat the PCH before running the tests... Now it actually completed the full OSX install and I'm able to use the laptop.. So far for 10 mins, no shut downs and no screen malfunction.....

        Has anyone had issues with the PCH without any liquid damage?
        Attached Files
        Last edited by bjhawfam; 06-30-2018, 09:48 AM.

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          #5
          Re: MacBook 820-3332-A turns on ,,,, than off with 3 beeps..

          I have the same board with the same problem! don't you love it when you post this stuff and no one leaves a reply? was your issue the PCH or did you throw the towel in?

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            #6
            Re: MacBook 820-3332-A turns on ,,,, than off with 3 beeps..

            Resolder U8900 it is a common problem with this board.

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